1. Field
The disclosed concept relates generally to electrical switching apparatus and, more particularly, to arc chute assemblies for electrical switching apparatus.
2. Background Information
Electrical switching apparatus, (e.g., without limitation, circuit switching devices, such as switches with and without fuses, and other circuit interrupters, such as circuit breakers, contactors, motor starters, motor controllers and other load controllers) typically include separable electrical contacts that are movable into and out of physical and electrical contact with one another when it is desired to energize and disconnect, respectively, a power circuit. That is, when it is desired to interrupt the power circuit, the separable electrical contacts are separated. Upon initial separation, an electrical arc is formed in the space between the contacts. The arc provides a means for smoothly transitioning from a closed circuit to an open circuit, but produces a number of challenges to the electrical switching apparatus designer. Among them is the fact that the arc results in the undesirable flow of electrical current through the electrical switching apparatus to the load. Additionally, the arc, which extends between the contacts, often results in vaporization or sublimation of the contact material itself. Therefore, it is desirable to extinguish any such arcs as soon as possible upon their propagation.
To facilitate this process, some electrical switching apparatus include arc chute assemblies which are structured to attract and break-up the arcs. For example and without limitation, a number of movable contacts of the electrical switching apparatus are mounted on movable arms which pivot the movable contacts past or through arc chutes as they move into and out of electrical contact with corresponding stationary contacts. Each arc chute assembly includes a plurality of spaced apart arc plates mounted in a wrapper and/or coupled to the electrical switching apparatus housing. As the movable contact is moved away from the stationary contact, the movable contact moves past the ends of the arc plates, with the arc being magnetically drawn toward and between the arc plates. Arc chute assemblies and, in particular, the arc plates of the arc chute assemblies are designed to encourage the arc to enter the arc plates. For example, it has been known to provide the arc plates of the arc chute assembly with a throat geometry, such as a U-shape or V-shape, which is structured to attract the arc away from the separable contacts into the arc plates. Specifically, the U-shape or V-shape plate geometry results in the formation of an arc-induced magnetic field, which draws the arc into the arc chute assembly where it may be effectively split among the arc plates into a series of smaller arcs and dissipated until the electrical current of the arc is extinguished. Examples of arc chute assemblies and arc plates therefor are disclosed in U.S. Pat. Nos. 7,521,645; 7,094,986; and 7,034,242.
There is room for improvement in electrical switching apparatus, and in arc chute assemblies therefor.